Refrigeration method and apparatus



sept. 1s, 1930. L, U, LARKjN 1,576,235

REFRIGERATION METHOD AND APPARATUS Filed June 28, 1928 4 Sheets-Sheet l A gwvvmtoz f Lgsfgr zLLff/ein agg/MW 4 Sheets-Sheet 2 Filed. June 28. 192B III f I un I y@ I I I 1 I I TL. I I I l I l I I +L I I IL. L I I I L TL. I l I I I I I I A M/ I I l u l- \nr E 5 Jin h 6 ,t A@ a@ 2W sept. 1s, 1930.

L. U. -LARKIN REFRIGERATION `METHOD AND APPARATUS Filed une 28, 192e 4 sheets-sheep s,

IM/vanto@ [1195135111 ZI. Larkin y Sept. 16, L. U. LARKIN l l REFRIGERATION METHOD AND APPARATUS Filed June 28, 1928 '4 Sheets-Sheet 4 Leser U. Larkin Patented Sept. 16, 1930 UNITED STATES LESTER. U. mam, orA'rLAN'rA., GEORGIA REFBIGEBATION METHOD AND APPARATUS Application led June 28,

general and" particularly to cooling units adapted for use in display case refrigerators, refrigerator cars, storage rooms, household refrigerators, etc.

In cooling units, heretofore commonly used, it has been customary to solder tinned copper heatabsorbing plates to tinned copper cooling tubes extendin lengthwise and in contact with the sides o plates; which is obviously an expensive and time consuming method.. Moreover the solder interposes a contact medium between the absorbing plates and the cooling tubes which is of less heat conductivity than the plates and tubes; and therefore retards, to some extent, the iow of heat from the absorbing plates into the cooling liquid in the tubes.

In the most eiicient units heretofore used, the ratio of cooling surface of the absorbing plates to the radiating outer surface of refrigerators has been largely a-matter of guesswork; and, generally has been such as to requi're a large difference between the temperature of the cooling units and the temperature maintained at the center of the refrigerator casing. -In refrigerators for preserving meats and the like, the result arlsing from this'great temperature dierence is very inefiicient;meats lose a great deal of weight by" dehydration due to exposure to below freezingl temperature, and due also to the high,y rate ofair circulation caused by this great temperature difference.

ing tubes, have been made. These tests, made 4withan 8" x 6 x 10 well insulatedv cooler,

show that in order to maintaina temperature of 36 degrees F., one half way up in the coolring compartment, itis necessary to maintain a temperature ofnot less than 21 degrees on the absorbin plates. This results in heavy frosting of t e absorbingl plates wlth consequent reduction 1n eiiicience and dehydration 1928. Serial No. 288,824.

of' the meats, etc., exposed to rapidly circulating air at very low temperature.V

As the desired temperatures to be maintained decreases, the temperature differences, with prior coils, increase. For example, in al 12 foot display case with the mostwidely used coils at the ends thereof, it has been found that in order to `secure a temperature of 32 degrees at the center of the case, it is necessary to' reduce the-temperature' of the end coils to at least 8 degrees, with the concomitant quick and heavy frosting and reduction in efficiency.

The ymain object of the present invention is to provide a cooling unit capable of being manufactured at a much lower cost than any unit of corresponding cooling power heretofore known and used, and which, in its use,

eliminates all the undesirable effects resulting from use of prior cooling units. The decrease in costof manufacture of the present vcooling unit results from the substitution of aluminum heat absorbing plates for the cop per plates heretofore used.

Contrary to general understanding, actual tests demonstrate that aluminum has a greater rate of heat conductivity and absorption than copper. Long bars of copper and aluminum, identical in all dimensions and having one end of each exposed to the same temperature for a given'time show that the other end of the copper; rises in temperature nearly twice as fast a's the corresponding end of the aluminum bar. Tests of this nature have given rise to the commonly ac'- cepted idea that copper has nearly twice the heat conductivity of aluminum. This result is due, however, to the fact that the aluminum -radiates heat much faster than copper.

bars of each metal, actual te'sts demonstrate l that the temperature of .aluminum rises more rapidly than copper exposed to the samedegree ofheat; it is also found that it loses its temperature more rapidly than copper.

This property'of aluminum involving rap-` id absorption and radiation of heat is taken advantage of in the resent invention, where'- in aluminum heat a sorbing vplates are substituted for the copper plates heretofore used.

a coating for cop One great difficulty, however, arises in using aluminum plates as heat absorbers on copper tubes. Aluminum cannot be soldered to any metal by any cheap owing solder; and the joints formed by any solder known at present will not stand up and are altogether very unsatisfactory. Moreover, the solder forming this joint acts as a heat insulator and thereby decreases the eiliciency of the cooling unit.

In order to avoid the expensive and unsatisfactory job of soldering aluminum heat absorbing p ates to the cooling tubes, the aluminum plates .are mounted perpendicularly to the cooling tubes, and are forced or shrunk thereon, without soldering, to form a' very tight joint between the plates and tubes. In formin the joint, say for an aluminum plate of o. 24 U. S. S. gage on a 5/8 inch tube of aluminum, copper, or other metal, it is preferable to draw the plate at the center point of the joint; then punch a one-eighth inch hole cleanthrough the center of the depression formed by the drawin Next, the metal around the punched hole 1s drawn and expanded until a cylindrical flange of about lg inch'in diameter and one-half inch deep projects from the face of the aluminum plate. The plate is then forced over the tube to the position desired, and is held in such position y the friction between the'cylindrical flange and the tube.

The aluminum plates may be heated before being applied to the tubes in order to expand them and their joint openings to facilitate application ofthe plates to the tubes. When the plates, mounted hot on the tubes cool, they shrink on to the tubes and the joint becomes extremely tight and heatconductive.

Theoretically itwould seem preferabletouse aluminum tubes as well as aluminum plates; but, the diiculty of soldering aluminum to aluminum or any other metal, practically prohibits such construction. The tubes must have their ends connected to a float tank re ulati the supply of cooling li uid to the tu es of t e unit. These tanks an the tubes connected thereto are usually made of copper, and tinned copper tubing is not only `ve readily soldered to the copper tank, but the soldering thereof costs a great deal less and makes a much stronger ointthan would be possible if aluminum'tu s were substituted or copper tubes. A.

While untinned copper may be used, the tinned copper tubing 1s so cheap that it is more economical to use it throughout, than it would be to use plain copper tubing and tin the soldered joints where such joints must be made. Moreover, since tin has the vsame coeicient of expansion as aluminum, its use as r tubin aids in maintainin the close riction joint between the absorbing late and the tubes.'

For the est results in using cooling units of the type disclosed herein, it has been found by actual test that the total surface area'of the heat absorbing plates should be'equal to the outside radiating surface of the chamber to be cooled and that the cooling tubes assing perpendicularly through these ates should be spaced not more than 31/2 inches between centers, and the edges of each late should be not more than 1% inches rom the nearest cooling'tubes.

There is an outer'margin of 1% inches bctween the outer edges of each plate and the nearest tubes, and the plates are bored to fill the space enclosed by this marcin with pipes spaced not more than 31/2 inches apart.

This resultsin the formation of a point at which the rate of radiationa'pproximately equals the rate of heat conductivity for the type of evaporator described in my application.

Preferably the tubes are 5/8 inches in diameter and of .625 inch tinned co per' and the aluminum plates or fins preferably o. 24 U. S. S. gage.

With units constructed as described and in the proportions described, with regard to the chamber intended to be cooled, it has been found by actual test that a temperature of 36 degrees F. can be maintained in the center of a 8 x 6 x 10. cooler by maintaining the coil with the temperature on the absorbing fins at between 34 and 35 degrees. The temperature difference vin'this case is less than two degrees. The most elicient of the prior coils now in common use requires a temperature difference of not less than fifteen derees to maintain the center of the same cooling at 36 degrees F.; that is the temperature on the cooling fins that must be held at not higher than 21 degrees.

It is of course to be understood that the present cooling unit must be arranged in the hottest part of the casing to be cooled and that the tubes must extend in a direction quently without freezing 0r dehydrating any of the contents of the casing whatever. The

very large surface area and rapid heat abvsorption of the aluminum plates all lead to a rapid temperature drop when the unit is A in operation. Since this temperature dro is less than two degrees, it follows that eac refrigerating cycle of o eration must be of very short duration, an consequently, must greatly reduce the amount of power required tomalntain it in operation. V Whatever little moisture may be picked up from the air inthe casing is deposited on the plates; and, because of the large surface area of these plates, must, when condensed, be spread on such plates in a ver thin film,

-which is constantly being remove by the circulatingair and returned to the air an meats from which it was taken.

Where below freezing temperature must be maintained on the plates, as in prior coolers, it is obvious that any moisture taken from the meats become condensed and frozen ony the plates and cannot be removed therefrom by the circulating air. In this case, the meats not only lose weight, which cannot be recovered, but also deteriorate greatly in quality.

This maintenance of humidity is only one of the most important results iiowingfrom A older coils. A

Otheriobjects and advantages of the invention will become apparent as the detailed description of :severalspecific embodiments thereof proceeds. Y

In the drawings: Fig. 1 is a' perspective view of a show case refrigerator cooled. by coils constructed according to this invention; v I

Fig. 2 is a side elevation of one form of cooling unit;

Fig. 3 is a plan of the unit shown in Fig. 1;

Fig. 4 is an elevation of one end of said unit; A

Fig. 5 is an elevation of the other end of said unit; Y

Fig. is a side elevationof a modified form of cooling unit;

Fig. 7 is a plan viewof the unit shown in y Fig. 6A;

Fig. 8 is a perspective view of' one ofthe aluminum heatv absorbing plates;

Fig. 9 is an elevation of one end of the said modified form of unit ;l Fig.- 10 is an elevation of the other end of the last named form;

Fig. 11 is a detail view of the joint between an aluminum heat absorbing plate and a copper tube passing therethrough; and

Fig. 12 is a view taken at right angles to the view shown in Fig. 11.

Referring to thel drawings:

Fig. 1 shows a refrigerator casing 1, 'of the 4 show case type, having improved cooling units 21nd 3 suitably supported at opposite ends of the casing 1.

`lla/ch unit shown'in Fig. 1 is illustrated in u `detail to a larger scale in Figs 2, 3, 4,'and \thereby aid 1n the circulatlor. of theJ cooling 5. s shown in saidgures each unit com- :`/liqu1d through the'colls. f A

prises-what is commonly known in this art, as a boiler 4. One end of boiler 4 is provided with. a valve 5 to control the admission of cooling liquidy from a condenser, or other suitable source of supply, into the boiler 4; and is also provided with a valve 6 to Icontrol the egress of vapor derived from the cooling liquid previously-admitted to said boiler, to a suitable compressor and other apparatus, designed to recondense the vapor to a liquid.

The boiler 4 is old; and valves 5 and 6,

and all the other mechanism, to control the ingress of condensed cooling liquid and the egress of vaporized cooling liquid to and from the boiler 4, are also old and well'known in this art; and for this reason are-not shown nor described in detail herein. The boiler 4 and valve mechanism carried thereby, however, do form a new combination with the cooling tubes and heat absorbing fins ar ranged to form the new refrigerating unit; and, the unit as a whole, arranged in the refrigerator casing in the particular manner disclosed and claimed herein, forms with said casing a combination producing new and useful results long sought for by persons skilled in this art.

As shown in Figs. 2 to 5, inclusive, of the drawings, the boiler 4 is intended to be arranged substantially horizontally with the liquid control valve 5 in the lowest position.

The cooling liquid is conducted from the lower part of boiler 4 through tubes 7, 8, 9 and 10, to the-lower end of a group 11 of heat absorbing plates 12 arranged vertically `and parallel to each other.

As shown particularly in Figs. 2 and 4, the ends of these tubes are connected,respec tively, to one end of U-shaped tubes 13, 14, 15 and 16, preferably by soldered joints commonly used to connect tubes together. Y g

Vertically arranged above the tube 13 are the similar U-shaped tubes 17 and 18, having their 'branches 19, 20, 21 and 22 parallel to the branches 23 and 24 of the tube 13. The

branch 23 is connected to branch 22 by a bend 25; branch -21 is connected to branch 20 by bend 26; and, finally branch19 is connected to the boiler 4 by a bend 27.

. The construction just described obviously,

.closed conducting circuit from and to the boiler 4. The tube 7 is connected to -thelowest branch 24 and the bend 27 connects the top branch 19 to the boiler ata point higher than the connection between boiler 4l and tube 7. This is to avoid heating of the cooling liquid by the plates 12 until the liquid in tubes 7 has reached its lowest point, and

Obviously, if the plates 12 were applied tol tube 7 at or immediately below the boiler, the

.absorbed heat would at once tend to vaporize the cooling liquid and would slow down the circulation through the, whole circuit. By leaving tube 7 free/of heat absorbing plates, the cold liquid falls rapidly by gravity to Y branch 24 and the 'plates 12 acting on this liquid tends to vaporize it and eiiect its re turn to the boiler 4.

.Vertically above the U-shaped tubes 14, and

y extending similarly through the plates 12 are the similar U-shaped-tubes 28 and 29 connected by bends 30, 31 and 32 to conduct the cooling liquid through the group of plates 12 to the boiler 4 at a point somewhat higher than the point at which the tube 33 conducts I 'liquid from the boiler to the lower branch of U-shaped tube 14.

The arrangement of U-sliaped tubes andwiththe heat absorbing plates 12 until they arrive at their f boiler.

lowest point remote from the `A modified form of unit is illustrated in Figs. 6, 7, 8 and 9. In this form the boiler 34 has itsaxis parallel to the heat absorbing plates 12 and perpendicular to the tubing passed through said plates.

The cylindrical side of boiler 34, remote from the group of plates 12 is provided with a valve. 35 to control the egress of vaporized cooling liquid from boiler 34, and with a valve 36 controlling the supply of coolin liquid to said boiler. These valves andthe anismv controlling the level of the liquid `iin the boiler, are old, and thespecifc details thereof constitute no part of the present invention. The novelty in this, as in the previously described form, resides in connecting the pipes conducting the cooling liquid from thelboiler 34 directly ,to the bottom or colder part of the boiler and in connecting the vapor return pipes td the boiler at higher parts thereof.h

As in the previously -described embodiment,

vthe pipes conducting the cooling liquid from .the'boiler to the group of cooling plates are not connected to said plates unt1 they have reached their lowest point remote from the These constructions eliminate the possibility of heat derived ,from the plates 12 or 12 from retarding the How ,of coolin liquidfrom the tanks, and permits the liquidil C In Fig. 5, the flrst vertical tien'of oat mechto rfall by gravity, and in its coldest state, until it enters the group of heat absorbing plates at the lowest point.

In the second embodiment of the invention a bank of ei hteen pipes are connected to the bottom of the boiler 34, which is normally Vertical; and, at various distances from said bottom, these Vpipes arebent to form horizontal branches extending through the grou 11 of heat absorbing plates 12. A secon bank of-eighteen pipes are passed per endicularly through the upper half of sai group 11vl and are connected to the cylindrical side of said boiler to return vaporized cooling liquid to the boiler.' The second bank of pipes are connected to the iirst by vertically arranged U-shaped bends soldered to the ends of each bank. As these. outflow and return pipes are .symmetrically arranged en need be described herein, as the tiers aresimilar and are similarly arranged.

pipes comprises the three outlet pi es 37, 38 and 39 connected to the bottom o boiler 34 and Ithese pipes are bent to form horizontal branches/40, 41 and 42, respectively, which pass\perp endicularly through the lower half of the group 11 of plates 12. Vertically arranged above thes'e branches 40, 41 and 42 lare the return branches 43, 44 and 45, assed through the upper halt` ofi group 11 o lplate 12 and bent to connect with the cylindrical` side of boiler 34.

The lowest outlet branch 40 is connected.

44, while the bends 46 and 48 are curved to provide'V for proper connection, around ranches 40 and 44, to the branches 42, 43

formed of aluminum and the tubes are made of tinned copper. opper is preferred for the tubing because of its non-corrosive prop erties; and because it can be very easily'soldered to the boilers and to the bends connecting the ends of one branch to another; The aluminum plates cost about one thirdof theprice` of .copper plates of the same dimensions; are more easily cut, punchedl andvdrawn, than copper platesgare much lighter; and,`actual tests, show the aluminum radiates and absorbs heat more rapidly *than copper.

While the prior art in a somewhat related field, shows that heat absorbing fins have vbeen arranged perpendicularlyl across a invention is employed aluminum plates have never been used for heat absorbingpurposes, because prior heat absorbingl plates, where used, were invariably soldered to the sides of the tubing, and because the cost of soldering such plates, if made of`aluminum, would be wholly prohibitive, and the joints poor. Moreover, these aluminum plates had never been used previously, because it was 'the general impression in the art that aluminum was a poorer conductor of the copper commonly used.

By actual test it has been discovered that aluminum plates absorb and `radiate heat more rapidly thancopper and this is the main reason for the selection of aluminum in the present invention. The difficulty 'of connecting aluminum to copper is overcome by heat than lthe following method.

Each of the aluminum plates 12 or 12 is first slightly-drawn at the points where the tubes are to pass `through and a hole of about one eighth inch in diameter is punched through the center of each depression formed by the first drawing operation. The drawn parts are then further drawn and each hole is enlarged to about nine -sixteenths and a flange49 about one-half inch deep is formed to project ,from one face of the plate. i

In' this case the plates 12 are intended to be forced on tubing five-eighths inch in diameter. The flanged plates may be preheated to cause their flanged apertures to expand,

and in this heated condition may be slid on tof the tubing and allowed to cool. The cooling causes the aluminum plates to shrink and engage the copper tubes with enormous pressure which practically insures a perfect heat conducting Joint between the plates and tubing. The tinned copper tubing and aluminum have substantially the same co-efiicient ofexpansion, so that the joints once formed as described, remain effective throughout the rangesof temperature to'which theco'oling units may be exposed.

The cooling units of thisinvention must be arranged with their fins vertical and parallel to the direction of air circulation in the inch casing or chamber where the are installed. This isillustrated clearly in ig. 1 where the units 2 and 3 areshown as mounted with their Icooling tubes horizontal and with the absorbing 'fins parallel to the lon-g axis of the case 1.

The form of cooler unit shown in Fi 1 is to be preferred where the units must ge arranged across a comparatively narrow casing, and access may be had to the boiler 4 from the top of the casing. The other form is adaptedto be used 'where a long narrow unit is'necessary, as in counter cases 4having air circulating from 'front to rear insteadA of from end to end. f

lThere is a decidedly new result obtained b positioning units ef this type in the manner described in refrigerator casings. The very large cooling area of the heat absorbing fins absorbs heatvery rapidly andconsequently greatly decreases the duration of refrigeration cycles necessary to maintaina given temperature.

Where the casings are properl insulated, l'

with five-eighths inch copper tu ing spaced ap art at V3 1/2 inch between centers through aluperature of 36 degrees F. can beunalntained at the center of the casing by maintaining Ia temperature of 34 degrees F. on the fins of the cooling units. Since this is abov'efreezing point, this temperaturelof 36 degrees can be maintained without frosting the fins. It is obvious, too, that any moisture condensed on'th'e fins will be removed, practically as fast as formed, by the air circulating through they units; since this moisture' must, because of the large condensing area 0f the4 fin, be formed in exceedingly thin films which can be readily absorbed by the circulatlng a1r. The rapid rate of reduction in temperature by the units,and the small difference in the temperature between the temperature to be maintained in the casing and that on the cooling fins, obviously greatly reduces both the time and cost of operation in comparison with the known cooling units involving a temperature difference of not less than fifteen degree`s.-

The elimination of soldered joints and braces between absorbing plates and tubes also greatly decreases the cost of manufacture, yin comparison with prior devices requiring the soldering of the plates to the sides' of the tubes.

Having described the advantages involved in the manufacture and use of the present invention, and having fully disclosed the method of manufacturing it, what I now claim and desire to secure by Letters Patent is:

1. In a refrigerator, the combination with a chamber designed for the circulation of air in a given direction therein, of piping in said chamber having branches thereo extending in a direction substantially perpendicular to the direction of the circulating air, heat-ablll f branches and in heat-absorbing contact thereals with and means for circulating a cooling fluid throu h said piping.

2. Align a refrigerator, the combination with a chamber designed for the circulation of air therein. in a given direction, of a boiler mounted in said chamber and having valve mechanism controlling the ingress of cooling liquid thereto and the egress of vaporized ycooling liquid therefrom, piping extending rom said boiler to form a circulation path for said cooling liquid, heat. absorbing iins connected perpendicularly to said piping and arranged in said chamber parallel to the direction of air circulation in said chamber.

3. In a refrigerator, the combination with` a chamber designed for the circulation of'air' in a given direction therein, a'bank of heatabsorbing plates arranged in said-chamber parallel to the said direction, piping passing erpendicularly through said plates and in heat-absorbing contacttherewith, and means for circulating a cooling fluid through said Piping- 4. In a refrigerator, the combination with a chamber designed for the circulation of f air in a give direction therein, a bank of heat-absorbin plates mounted in said chamber parallel to the said direction, a valve controlled tank for cooling liquid, piping connected to the lower part of said tank to conduct cooling fiuid to the lower part of said bankof lates, and means to return said cooling flui` from said piping perpendicularly through said bank of plates to said tank.

5. In a refrigerator, the combination with a casing having heat insulated walls, of a cooling unit mounted in said casing and comprising piping having a cooling liquid circulating therein, a bank of heat-absorb- .ing plates connected to said piping and having a cooling contact area for the air in said casing equal to the area of the putside of said casin u 6. In a refrigerator, the combination with Y a heat' insulated casing of a tank mounted therein and having valves controlling the admission of cooling liquid to said tank and the release of vaporized cooling liquid therefrom,

.a bank of heat absorbing plates mounted below 'said tank parallel to each other and substantially vertical insaid casing, a pipe connected to the lower part of said tank and extending to the lower part of said bank of plates, and piping connected to said tank and to the lowest end of said pipe, and having parts thereof extending perp'endicularly through said bank of plates.

7. In a refrigerator,- a refrigerating unit comprisinl piping for a refrigerant having substantia ly parallelbranches, and substantially parallel spaced heat absorbing fins secured substantially perpendicularly to said branches, said unit being arranged with the fins approximately vertical, and means forming a chamber enclosing said unit, the walls of said chamber being posi- 'refrigerant therefrom, piping extending substantially horizontally from said boiler toform a circulation path for-said refrigerant, heat absorbing fins connected substantially perpendicularly to said piping, and means forming a chamber enclosing said unit, the walls of said chamber being positioned to determine a circulation of the air in said chamber induced by the convection iow of air between said fins.

9. In a refrigerator, a refrigerating unit comprising a bank of spaced heat absorbing plates arranged approximately' vertical, piping passing substantially perpendicularly through said plates and in heat absorbing cont-act therewith, means for circulating a refrigerant through said piping, and means orming a chamber enclosing said unit, the walls of said chamber being positioned to determine a circulation of the air in said chamber induced by the convection How of air between said plates.

10. In a refrigerator, a 4refrin'erating unit comprising a bank of spaced Iieat absorbing plates mounted substantially vertical, a valve controlled tank for a refrigerant, piping connected to the lower part of said tank to conduct a refrigerant to the lower part of said bank of plates, means to return said refrigerant from said piping perpendicularly through said bank of plates to said tank, and means forming a chamber enclosingsaid unit, the walls of said chamber being positioned to determine a circulation of the air in said chamber'induced by the convection How of air between said plates.

11. In a refrigerator, a refrigerating unit comprising piping for circulating a refrigerant horizontally arranged, a bank of heat absorbing plates arranged approximately vertically and connected to said piping, and means orming a chamber enclosing said unit, the walls of said chamber being heat insulated, said walls being positioned to determine a circulation of the air in said chamber induced by the convection flow of air between said plates, the aggregate area of said plates being approximately equal to th area of the walls of said chamber.

12. In a refrigerator, walls enclosing a refrigerating chamber, and a refrigerating unit therein having heat exchangin fins, said fins having an aggregate area su tantially equal to the a gregate area of the ber, so as to produce eiiicient refrigeration within said chamber at a temperature differential between said Vunit and the atmosphere in said chamber so small as to avoid frosting,

-of said refrigerating unit.

12% In a refrigerator, walls enclosing a, refrigerating chamber, and a refrlgerating l unit therein, said unit including heat exchanging aluminum fins having ,an aggregate area substantially equal to the aggre-4 gate area of the bounding surfacesof the refrigerating chamber, so as to produce eiicient refrigeration within said chamber at a temperature differential between 'said unit and vthe atmosphere within said chamber so small as to avoid frosting of said refrigerat-- ing unit. v

14. In a refrigerator, walls enclosing a refrigerating chamber, and a refrigerating unit' therein including substantially horizontal pipe sections and a plurality of fins in heat exc-hanging relation to said pipe sections and perpendicular thereto, said fins having aggregate area of said walls as to produce eiiicient refrigeration within said chamber at a temperature differential betweensaid unit and the atmosphere within said chamber so small as toi/,avoid frosting of said re.`

frigerating unit.

l5. In a refrigerator, walls enclosing a refrigerating chamber, and a refrigerating unit therein including substantially horizontal pipe sections and a plurality of aluminum fins'perpendicular to said pipe sections and 'i in heat exchanging relation thereto, said fins having an aggregate area so definitely related to the aggregate area of said walls as to produce eiicient refrigeration within said chamber at a temperature differential `between said unit and the atmosphere within said chamber so. small as to avoid frosting of I i said refrigerating unit.

16. In a refrigerator, walls enclosing a refrigerating chamber, and a refrigerating unit therein, including a' pluralityof substantially horizontal pipe sections and a plurality of aluminum fins arranged perpendicularly to said pipe section and in heat exchang-v ing relation thereto,.the aggregate area of said fins being substantially equal to the aggregate area of said walls so as toV produce.

efficient refrigeration within said chamber at atemperature' differential between said unit and the atmosphere within` said chamber so small as tb avoid frosting` of said refrigerating unit. i

, 17. In a'refrigerator, walls enclosing a refrigerating chamber, and a refrigerating unit therein comprising anevaporator coil having a plurality of substantially horizontal pipe v sections and a plurality ofaluminum fins,-

each iin being common to said pipe sections l and arranged perpendicularlv thereto in heat 65.

exchanging relation therewith, said' fins havanl aggregate area so definitely related to theing an aggregate area so definitely related to the aggregate area of said walls as to produce efficient refrigeration in said chamber `at a temperature differential between said unit and the atmospherewithin said chamber so small as to avoid frosting ofsaidre-vfr1gerat1ng unit.

18. In a refrigerator, walls enclosing a refrigerating chamber, and a refrigerating unit l therein comprising an evaporator coil including a plurality of substantially horizontal pipe sections, a plurality of aluminum fins each tin being common to said pipe sections and arranged perpendicularly thereto and in heat exchanging relation therewith, said pipe sections being spaced in said fins so as to occupy the centers of the contiguous areas at whose bounds the rate of radiation approximately equals the rate of heat conductivity.

.19. In a refrigerator, walls enclosing a -refrigerating chamber, and a refrigerating unit therem comprising an evaporator coilA including. a plurality of substantially parallel pipe sections, 'a plurality of/aluminum tins, each fin being common to said pipe sections, said plpe sectlons being spaced 1n sald ns so as to occupy the centers of contiguous areas at whose bounds the rateof radiation approximately equals the rate of heat conductiuity.

20. In a refrigerator, walls enclosing a.

refrigerating chamber, and a refrigerating unit having'l substantially horizontally dis-` posed'pipes, and substantially verticallyl disposed heat exchanging Iinsrperpendicular to said pipes, said fins having an aggregate area so definitely related to the aggregate area of the bounding surfaces of said refrigerating Y chamber, that etticient refrigeration temperature is maintained in said chamber by the maintenance of a fin temperature not materially lower than 32 degrees F; whereby frost does not `form on said refrigerating unit.

omprising. a continuous pipe conduit for re- Ifrigerant having a plurality of substantially vmine a focal region in said refrigerator for originating and maintainlng a defii'nte con-v 21. Ina refrigerator, a refrigerating unit lVection circulation of air within said refrigerator.

22. In a refrigerator, a refrigerating unit comprising a continuous pipe conduitfor refrigerant having a plurality of substantially parallel portions arranged in a plu@ rality of super-posed substantially horizontal banks` with a plurality of said portions in -each bank,heat absorbing fins'each comnoon 'to al1-said portions disposed perpendicwith each of said pipe limbs.

- 2&.In combination'with an evaporating x tank, a pipe loopconnected at its ends to said tank and having parallel-limbs extending Substantially horizontally, andthin Vsheet metal heat absorbing fins extending perpendicularly'to said limbs and in heat absorbing contact with at least one of said limbs.

25. The combination with an evaporator tank having mechanism to control the admission of condensed cooling fluid thereto and the suction of vaporized cooling fluid therefrom, apipeconnected to and extendingsubstantially horizontally from said tank to conduct cooling 'fluid therefrom, a second pipe connected to said tank and extending parallel tothe first named pipe to return to said tank the Huid passed through the first named pipe -a heat absorbing fin extending perpenarl 'to and in I dieu eatabsorbing contact with each ofsaid pipes, and means for conducting said'fluid from the. end-of the-first named pi e remote from said tankl to the correspon ing endof the othertank.

' 26. The combination with an evaporator tank having mechanism to control the admission of condensed cooling Huidl thereto and the suction of vaporized cooling-fluid therefrom, of a heat absorbing n,.pipes connected to said tank and extending substantially horizontally and parallel to' eachother perpendicular-ly' throughA saidin'andin heat absorbing contact therewith, and means for .s conducting cooling fluid-from some 'of 'said pipes to others to' return the cooling Huid 50 through said other pipes from the irst named pipes. l. l

7. In arefrigerating plant, a valve controlled evaporatin'g' tank, piping having :its opposite ends connected to said 'tank and' having parts thereof substantially horizontal andv` arallelto each other, andheat'absorbing ns -spacedalong said parts perpendicularly thereto and in therewith.

28. In a refrige'rating plant, an evaporathrou hand-in heat absorbing contact with' said 1111s, and means connecting the ends of said pipes remote from said tank to conduct cooling fluid from some of said pipes to others. l

29. A container for 'cooling liquid, copper pipes having one end of each soldered to and extending from the container to conduct said liquid from and return'it to'saidcontainer, said pipes having horizontally disposed lparts thereof parallel to each other, aluminum fins extending perpendicularly to all of said `parts and held by friction in heat conducting contact therewith, and means soldered to the other ends of said ipes to provide passage Y for said liquid etwe'en the said conductingand return pipes.

. .30. A -cooling-unit comprising a valve controlled evaporator 'float tank for cooling liquid, a group'of pipes connected to sai tank to conduct cooling liquid therefrom, af'

second group of pipes connected to said tank to return fthe liquidto said'tank afterpassage through the first named group, means connecting the free ends of said group to conduct liquid from'the first named group to the second, all of said pipes being parallel to eachother and substantially horizontally clisposedand heat absorbing ns secured perpendicularlyto eachof said p'i es and in heat conducting contact therewit 31. A combination with lan evaporator tank having mechanism to' control the admis-- sion 'of cooling liquid thereto and the suction of vaporized coolin liquid therefrom, heat absorbing vertical nsl parallel to each other, tubes .extending vertically from 'the lower part of said fins to conduct cooling iuid by gravity therefrom and-having parts bent arallel to each other and passing'perpendicularlv throughand in heat conducting contact wit said fins, tubesconnected to a 'higher part of said tank than the irst named tubes to return vaporized cooling'iuid tosaid tank and also having parts parallel to each Votherand passin perpendicularly7 through and in heat absor ing contact wit said fins abogvlthe parallel parts Lof the first named tube, means for 'conducting cooling liquid from the vfirst to the Vsecond named tubes, the parts of said conducting tubesentering. said ns at their points remote from said tank.- V

j In testimony whereof 'I afiixmy signature. V 4 LESTER U. 'LARKIN heat conducting-contact p tor: comprising avvalvecontrolled tankv for f cooling fluid, heat absorbing Vfins parallel'to ...each other, pipes connected to said tank and extending substantiallyv horizontally and parallel to each otherV perpendieularly fi if 

